Determination of rituximab dose according to immunologic risk in ABO-incompatible kidney transplantation

The adequate rituximab (RTX) dosage in ABO-incompatible transplantation (ABO-IKT) remains undetermined. We used two kinds of RTX dosage groups [low RTX (100 mg/m(2)) and typical RTX (375 mg/m(2)) dosage groups] according to immunologic risks and investigated the change of B-cell, anti-ABO antibodies, and the clinical outcome in ABO-IKT according to the RTX dose. Fifteen patients with high immunologic risk [panel reactive antibody (PRA) > 50%, retransplant, AB to O transplant] were assigned to typical RTX group and 17 patients without risk were assigned to low RTX group. We compared the changes of B-cell, anti-ABO antibody titer, required number of plasmapheresis (PP), and the clinical outcome after transplantation between the two groups. After infusion of RTX, peripheral blood B-cell counts were successfully depleted to <1% in both groups. Before kidney transplantation (KT), the minimal number of PP to achieve the target titer (1:16) (2.6 ± 2.7 vs. 2.2 ± 2.5; p = 0.66) and the titer reduction rate of anti-ABO antibodies did not differ between the two groups (low RTX: 1.52 ± 1.21 vs. typical RTX: 1.53 ± 1.20, p = 0.94). After KT, anti-ABO antibody titer was suppressed less than 1:32 in both groups up to posttransplant 1 year. The allograft function and infectious complication did not differ between the two groups as well. In ABO-IKT, low RTX is comparable with typical RTX dosing with respect to B-cell depletion, antibody rebound suppression, the effect on clinical outcome in patients with low immunologic risk.